1. Field of the Invention
The present invention relates generally to control of turbochargers used in engines with Exhaust Gas Recirculation (EGR) systems, and more particularly, to an intelligent electric actuator with diagnostics and memory capabilities using turbocharger rotational speed, air and EGR gas temperatures, and air and EGR gas pressures, for control of a variable geometry turbocharger with integrated EGR valve.
2. Description of the Prior Art
Commercial diesel vehicles typically employ turbochargers for increased efficiency of the engine. Further, the regulatory requirements for decreases in federal NOx emissions levels for year 2002, and beyond, diesel engines have made engine air systems control a more complex and important part of overall engine performance. Control of the turbocharger and EGR systems of the engine comprise the primary means for such air systems management.
A turbocharger""s useful life is, among other things, largely a function of the speed/duty cycle to which it is subjected, specifically with respect to the fatigue life of the turbine wheel and compressor wheel (or perhaps an internal component of the turbocharger). It is very difficult to know exactly what particular speed/duty cycle the turbocharger is subjected to for any given application. This therefore makes it very difficult to predict what the useful life of the turbocharger will be with respect to fatigue related failures. Therefore, fatigue failures of turbocharger wheels can and do occur without notice. Proactively replacing the turbocharger at a xe2x80x9csafexe2x80x9d accumulated time is not cost effective and results in excessive downtime of the engine.
The present invention is applicable to a controlled turbocharger such as, but not limited to, a wastegated turbocharger or a variable geometry inlet nozzle turbocharger (VGT) with an actuator to operate the wastegate or VGT vane set. By inputting the turbocharger""s shaft speed, air gas temperatures, air gas pressures, EGR gas temperatures, and EGR gas pressures into the intelligent electric actuator, this data can then be used as to better control the actuation of the wastegate or VNT nozzle set.
The software employed by the controller is designed such that various min/max speeds, temperature and pressure thresholds are pre-set with the subsequent excursions of speed, temperature and pressure recorded as these thresholds are achieved and/or exceeded.
An array of thresholds is pre-determined for the particular application. This data is stored in the actuator""s memory for future use. By defining the fatigue life of the compressor wheel or turbine wheel for a given wheel design, size, material, etc., and having the specific fatigue life information programmed into the REA, several advantages exist.
From the inputs of speed, temperature and pressure, the electric actuator is better used to more precisely control the turbocharger""s wastegate or VGT nozzle set. This information is also used to control EGR percentage directly and therefore control engine out emission level more precisely.
Once a predetermined number of speed, temperature and/or pressure thresholds have been achieved, the electric actuator can, in various embodiments, control (reduce) the speed of the turbocharger by predicting when a wheel fatigue failure is imminent.
Once a predetermined number of speed, temperature and/or pressure thresholds have been achieved, the electric actuator can, in various embodiments, trip a switch to notify the operator to xe2x80x9creplace the turbochargerxe2x80x9d by predicting that a fatigue failure is imminent.
The electric actuator can store into memory operational field data for future use in maintenance profiling of specific turbocharger operating conditions of various applications (on-highway truck, inner-city truck, pleasure craft, tug boat, front-end loader, bulldozer, mine truck, excavator, gen-set, etc.).
The speed/duty cycle data stored in the electric actuator can be down loaded and used in the warranty adjudication process or as a diagnostic tool for failure evaluation.